Flow and swelling behavior was investigated for poly(vinyl alcohol) (PVA) gel in the solvent flow field. It was found that the PVA gel swelled under solvent flow and the volume of the gel increased with increasing solvent pressure. The flow rate also increased with increasing solvent pressure. On the other hand, the characteristic times determined by swelling and flow kinetics were independent of the applied pressure, and were almost identical, suggesting that the swelling and flow properties of the gels were closely related to each other. A new type of diffusion equation, which can describe the time evolution of flow and volume change of polymer gels under flow, was proposed in this paper. Comparison between experiment and theory showed that the experimental results were explained fairly well by the theory.